U.S. Pat. No. 4,735,504 describes a method of acquiring two types of forward scattered lights having different scattered angles, a low angle forward scattered light and a high angle forward scattered light, and calculating hemoglobin concentration and capacity of red blood cells from the index of refraction thereof. However, the technique of accurately discriminating the red blood cells from the blood cells in the blood sample is not described.
U.S. Pat. No. 5,891,731 describes a technique of classifying the blood cells in the sample to red blood cells, reticulocytes, white blood cells, and blood platelets by specifically staining the reticulocytes and the white blood cells in the blood sample.
However, in the method of U.S. Pat. No. 5,891,731, a stain for fluorescence staining the reticulocytes and the white blood cells is used. When staining the blood cells, the blood sample is dispensed into a predetermined container, and then, the stain is dispensed into such container to prepare a measurement specimen. In this case, a dispensing step of the stain is required to prepare the measurement specimen, and thus a method of discriminating the red blood cells from the blood cells easily and with fewer steps is desired.